The unique electrical, optical, and mechanical properties inherent to carbon nanostructures, such as single wall carbon nanotubes (“SWNTs”), have garnered tremendous interest in basic science and applied research (Avouris et al., J. Phys. B 323:6 (2002); Dai, Surf. Sci. 500:218 (2002); and Landi et al., Nano Lett. 2:1329 (2002)). The opportunity to exploit these properties depends on the successful characterization and manipulation of desired materials. In some cases, the necessity to utilize solution phase techniques is hindered by the inability to form stable SWNT dispersions. Many groups have resorted to functionalization strategies (Peng et al., Am. Chem. Soc. 125:15174 (2003); Kahn et al., Nano Lett. 2:1215 (2002)), including the use of polymers (Landi et al., Nano Lett. 2:1329 (2002); O'Connell et al., Chem. Phys. Lett. 342:265-271 (2001)), surfactants (O'Connell et al., Science 297:593 (2002); Matarredona et al., J. Phys. Chem. 107:13357 (2003)), and amines to assist in dispersing SWNTs (Chen et al., Science 282:95 (1998); Chen et al., J. Phys. Chem. B 105:2525 (2001); Chattopadhyay et al., J. Am. Chem. Soc. 125:3370 (2003)). However, these techniques may disrupt SWNT structure, alter electronic properties, or be problematic for subsequent removal (Ausman et al., J. Phys. Chem. B 104:8911 (2000)). Therefore, the dispersion of as-produced, high aspect ratio, raw, and purified SWNTs in a suitable solvent is necessary to enable more accurate solution phase analyses.
The most promising attempts at forming stable SWNT dispersions have been with organic amide solvents such as N,N-dimethylformamide (“DMF”) and N-methylpyrrolidone (“NMP”) (Ausman et al., J. Phys. Chem. B 104:8911 (2000); Krupke et al., J. Phys. Chem. B 107:5667 (2003)), and with 1,2-dichlorobenzene (“DCB”) for both HiPco and laser-generated SWNTs (Bahr et al., Chem. Commun. 2:193 (2001)). Calculation of the extinction coefficient at 2.48 eV (500 nm) for as-produced HiPco SWNTs in DCB was reported to be 28.6 mL·mg−1·cm−1 (Bahr et al., Chem. Commun. 2:193 (2001)). This is higher than the recently reported value of 9.7 mL·mg−1·cm−1 for arc-discharge functionalized SWNTs in CS2 at the same energy (Zhou et al., J. Phys. Chem. B 107:13588 (2003)). These results imply that variations exist for the extinction properties of SWNT materials, potentially occurring from differences in diameter distributions, purity, and/or solvent effects. Dispersion of SWNTs in organic amide solvents has been attributed to the availability of a free electron pair and high solvatochromic parameter, π*, although these characteristics are not sufficient, since they are also present in dimethyl sulfoxide (“DMSO”) which is inefficient at dispersing SWNTs (Ausman et al., J. Phys. Chem. B 104:8911 (2000)).
A variety of experimental methods can be employed in the fabrication of SWNTs (i.e. arc-discharge, chemical vapor deposition, and pulsed laser vaporization). However, each technique produces SWNTs with differing diameter, chirality distributions, and various amounts of synthesis by-products (Dai, Surf. Sci. 500:218 (2002)). In general, the by-products are the principal component of the as-produced materials or raw SWNT “soot.” By-products such as graphitic and amorphous carbon phases, metal catalysts, fullerenes, and carbonaceous coatings on the SWNTs may not only dominate the physical characteristics of the raw soot, but they also pose significant challenges in any subsequent purification (Chiang et al., J. Phys. Chem. B 105:1157 (2001); Chiang et al., J. Phys. Chem. B 105:8297 (2001); Dillon et al., Adv. Mater. 11:1354 (1999); Dillon et al., Mater. Res. Soc. Symp. Proc. 633:A5.2.1 (2001); Harutyunyan et al., J. Phys. Chem. B 106:8671 (2002); Moon et al., J. Phys. Chem. B 105:5677 (2001); Strong et al., Carbon 41:1477 (2003)). Further development of SWNT-based applications is expected to require material standardization, specifically with respect to electronic type and degree of purity. Consequently, there is a need to develop a method whereby the types, amount, and morphology of SWNT-containing materials can be accurately and precisely quantified (Arepalli et al., Carbon 42:1783 (2004)).
The present invention is directed to overcoming these and other deficiencies in the art.